The present invention relates to conveyors and, in particular, to conveyors wherein carriers riding on trolleys of the conveyor are accumulated, staged or banked at a compact location within the conveyor system.
Power and free type conveyors are utilized in many installations for conveying partially assembled goods from one point of assembly to the next, for conveying finished goods from an assembly location to a storage location, for conveying finished goods from a warehouse to a distribution point and the like. For some installations, it is important to provide an accumulation area for the carriers at a desired location. For example, there may be a work station just downstream from the accumulation area where an assembler can only work on a single structure being carried by one of the carriers. Hence, it is necessary to restrain the remaining carriers until the assembler has completed work on the one in front of him, at which time he can send it downstream and divert a second carrier to the work station from the accumulation area.
If there are many carriers to be accumulated at the accumulation area and, especially, if the carriers are very long, (for example, where the carrier is transporting an automobile body), then the length of conveyor required to accumulate these carriers becomes quite long. A lengthy section of conveyor utilized just as a location for accumulation is both expensive and may consume a great deal of space. Therefore, conveyor manufacturers have attempted to overcome this problem by inserting bias or side-by-side tracks that are positioned next to or near the main conveyor.
An example of such a system is shown in the Dehne U.S. Pat. No. 3,195,473. Another such system is shown in the Kernkamp U.S. Pat. No. 4,602,566. Each of these patents partially resolves the problem of carriers accumulating in an end-to-end train-like fashion by allowing them to accumulate in a side-by-side configuration wherein the carriers are aligned generally perpendicular or at least at a substantial angle relative to the main track. Such systems allow accumulation of the carriers in a relatively small area.
Both of the above noted systems, especially the Dehne system, works well for certain types of carriers carrying certain types of loads. However, the Dehne system does not work where the load on the carrier is wider than the trolleys associated with the carrier, since adjacent loads would unacceptably collide with each other before the trolleys of adjacent carriers were able to engage one another and effectively space the loads. To overcome this problem, it is possible to extend the length of the trolley to a length greater than the width of the load; however, this then takes away from valuable space along the length of the main conveyor line.
It also continues to be desirable in the conveyor industry to try to develop methods of further compressing the accumulation area and thereby reduce costly building space or to allow some of the space previously used for a conveyor to be used for manufacturing functions.